Grid Display Package:
This abstract class provides common implementation code for
drawing a GridObject object. The class will translate and
scale the graphics system as needed and then invoke its
abstract draw method. Subclasses of this abstract class
define draw to just display an object with a fixed size.

ScaledDisplay

draw

Draw the given GridObject object.
Subclasses should implement this method to draw the object in a
cell of size (1,1) centered around (0,0) on the drawing surface.
(All scaling has been done beforehand).